Blocking in mental and motor tasks during a 65-hour vigil.

The term "block" refers to those periods experienced by workers when they seem unable to make a response and cannot continue, even by effort, until a short time has elapsed. In this study blocking in mental work (addition, subtraction and color naming) was greatly increased after a period of prolonged sleeplessness, the most noticeable increase being observed after 40 hours for all subjects. Final test trials indicated a decrease in blocking for two of the three subjects who completed the vigil. Where this final spurt occurs it is evident that measurement at the beginning and at the end of a period of sleeplessness does not give a true picture of the changes produced by the vigil. Since sleeplessness was not continued to the point of exhaustion, the decrement in mental work is explained on the basis of failure to achieve motivation sufficient to overcome the subjectively increased thresholds of attention and effort. In contrast with the mental work, there was no increase in the number of blocks during tapping, and the blocks were fewer throughout. This is possibly to be explained as due to the fact that the subject was not motivated to work beyond a congenial pace. (PsycINFO Database Record (c) 2012 APA, all rights reserved)